Flexible joints are used in a variety of apparatus, such as machines, to connect components that may move relative to one another. One type of flexible joint is a spherical joint, wherein two components are connected for compound movements by a semi-spherical bearing having a journal mounted therein. A pair of annular seal assemblies may be disposed on either side of the journal to protect the joint from debris or damage from the environment.
Sealing may be particularly advantageous when the joint is used in certain applications, such as on off-highway machines where the environment may include high levels of dust and debris. A mining truck, for example, may use a four bar link suspension to connect a rear axle to a frame. Spherical joints may be used at the opposite ends of each link to connect to either the frame or an axle housing, and each spherical joint, in turn, may use two seal assemblies to seal the journal. Accordingly, a four bar link suspension may include sixteen seal assemblies, with each seal assembly intended to withstand the potentially large deformations experienced during operation of the typically large-scale mining truck while protecting the journal from the environment.
During operation, the links may pivot to permit the axle housing to move relative to the frame. Pivoting of the links may cause relative rotational movement about a journal pin of each joint and pivotal movement transverse to the rotational movement. The seal assemblies deform during the transverse, pivotal movement which may curtail the service life of the seal assemblies. Conventional seal assemblies typically include a pair of inner and outer retaining rings with an elastomeric seal extending radially therebetween. Such a seal configuration has not shown a satisfactory service life when exposed to the pivotal movements experienced during operation of the machine.
Some conventional seal assemblies attempt to reduce the amount of strain experienced during operation by radially swaging the seal. Radial swaging typically involves compressing the outer surface of the seal inwardly to pre-strain the seal. While radial swaging may effectively reduce some seal strain during operation, such strain reduction may be insufficient for certain applications where the seals may experience significant deformation, requires at least one extra step during manufacturing, and is overly costly.